Cleft lip and palate are extremely common congenital anomalies that have devastating consequences for affected individuals and their families. The developmental events that must be completed to shape normal development of the face are multistep and complex. For example, in order to form an intact secondary palate or roof of the mouth, embryonic primordia called palatal shelves project vertically into the oral cavity, reorient to a position above the tongue, and then fuse at the midline. Currently, we possess a wealth of knowledge about signaling pathways and transcription factors that control these steps in development, but have practically no knowledge of the molecules that exert the forces to shape the development of the face, and how signaling pathways connect to these effectors is mysterious. Based on our preliminary data, combined with recently published human genetics studies, we believe that non-muscle myosins are excellent candidate drivers of craniofacial morphogenesis. The non-muscle myosins are molecular motors that walk along, propel sliding, or produce tension on the actin cytoskeleton and are crucial for a number of cellular processes including cell migration, adhesion and cytokinesis, but their functions in craniofacial development and disease are not known. Here we propose a series of experiments to investigate the developmental roles for nonmuscle myosins in craniofacial development and orofacial clefting. We propose to use mouse genetics approaches in which the function of the nonmuscle myosins is disrupted in specific cell types to define their action. Further, we will use advanced imaging methods to observe the cellular consequences of their loss of function in mice. We then propose to identify the signaling pathways that regulate the activity of these motors in the context of palate fusion. These experiments will therefore connect known regulators with the downstream effectors providing a more complete picture of how normal development of the lip and palate occurs, and how these events are perturbed in congenital anomalies such as cleft lip and palate. We expect these studies to hold significant implications for the design of preventative and therapeutic strategies for this common class of congenital anomaly. PUBLIC HEALTH RELEVANCE: Cleft lip and palate are among the most common congenital anomalies but the effectors of the underlying morphogenesis are largely unknown. This application seeks to characterize NMIIA and NMIIB, actin motors with distinct cellular and tissue-specific functions during development, whose function has not been studied in craniofacial morphogenesis. This work should provide insight into the etiology of orofacial clefting, and directions for designing preventative or therapeutic strategies.